An estimate of how long marine mammals need to acclimate to captivity would permit more precise comparisons of husbandry practices, yet no quantitative analysis of acclimation has been performed. Therefore, we estimated the duration of acclimation to captivity for bottlenose dolphins (BD) and California sea lions (CSL) by comparing 5-d survival rates during the first 90 d of captivity with a survival rate based on days 91-365 in captivity. Wild-born BD (n = 1,270) and CSL (n = 1,650) acclimate to captivity in approximately 35 and 40 d, respectively, whereas captive born BD (n = 332) and CSL (n = 992) acclimate in approximately 50 and 40 d, respectively. When transferred between two institutions, BD (n = 911) acclimated in the same amount of time (45 d) as when first transferred from the wild, whereas transferred CSL (n = 336) acclimated more rapidly (15 VJ. 40 d) than when first transferred from the wild. Based on results from these two species, a 60-d acclimation period is recognized as a distinct interval of relatively high mortality that should be treated separately from long-term survival estimates when evaluating husbandry practices of ocean-aria and zoos.